1. Field of the Invention
The present invention relates to a Liquid Crystal Display (LCD) device and a driving method thereof, and more particularly, to an LCD device and a driving method thereof, which reduce the power consumption of a data driver.
2. Discussion of the Related Art
An LCD device controls the light transmittances of liquid crystal cells to display an image, according to a video signal.
FIG. 1 is an exemplary diagram illustrating an equivalent circuit of a pixel included in a liquid crystal display panel of a general liquid crystal display.
Since an active matrix type LCD device actively controls data by switching a data voltage supplied to pixels using a thin film transistor (TFT) formed per pixels as shown in FIG. 1, it can improve display quality of moving picture images. In FIG. 1, a reference numeral “Cst” denotes a storage capacitor for maintaining a data voltage charged in a pixel, a reference numeral ‘D1’ denotes a data line to which the data voltage is supplied, and a reference numeral ‘G1’ denotes a gate line to which a scan voltage is supplied.
In order to reduce direct current offset components and degradation of a liquid crystal, the aforementioned LCD device is driven at an inversion driving mode where a polarity is inverted between neighboring liquid crystal cells in a frame interval unit. However, according to the inversion driving mode, as a swing width of the data voltage supplied to data lines is increased and much current occurs in a data driver whenever a polarity of the data voltage is changed, problems occur in that a heating temperature of the data driver is increased and power consumption is increased rapidly.
Meanwhile, in order to reduce the swing width of the data voltage supplied to the data lines and reduce power consumption and the heating temperature of the data driver, a charge share control (hereinafter, referred to as “CSC”) scheme based on a charge share circuit is applied to the data driver. However, the effect of the CSC fails to reach a satisfactory level. This is because that charge sharing carried out between data increases the number of transition times of the data voltage even though the CSC scheme reduces the swing width of the data voltage.
In this respect, in order to reduce power consumption and the heating temperature of the data driver, a dynamic CSC scheme has been recently suggested together with a power control (hereinafter, referred to as “PWRC”) scheme. The dynamic CSC scheme reduces the number of transition times of the data voltage by carrying out charge sharing only when the polarity of the data voltage is inverted. The PWRC scheme controls the power of an output buffer of the data driving circuit.
However, although power consumption can be reduced by the aforementioned schemes, since the same power as that consumed for an active interval is consumed even for a vertical blank interval where no image is output between frames, the LCD device according to the related art has a problem in that unnecessary power consumption still occurs.
FIG. 2 is an exemplary diagram illustrating waveforms of various signals of a general LCD device.
Examples of signals input to a timing controller of the LCD device, as shown in FIG. 2, include a vertical synchronizing signal Vsync input in one frame period, a horizontal synchronizing signal Hsync (not shown) input in one line period, and a data enable signal DE displaying input of data.
After data of the last gate line of a frame are out, a vertical blank interval, to which data are not applied, generally occurs in a liquid crystal display panel for a certain time period before data of the first gate line of next frame are output. The other interval except for the vertical blank interval will be referred to as an active interval.
Meanwhile, as described above, since the LCD device of the related art drives the data driver at the same power option ‘001’ even for the vertical blank interval where data are not output, as well as the active interval where data are output, the power is consumed unnecessarily.
In other words, according to the LCD device of the related art, if a power option of a source drive IC (source D-IC) of the data driver is powered on and set once, it continues to be output at one fixed value ‘001’ without any change regardless of the vertical blank interval and the active interval.
Generally, considering RC resistance of the LCD device, the fixed value is set to a normal power mode or more. In this case, the same power mode as that used during output of real data is used even for the vertical blank interval where real data are not output, whereby unnecessary power consumption occurs in the LCD device.
In other words, according to the LCD device of the related art, the same source drive IC power option ‘001’ is used regardless of the vertical blank interval and the active interval, whereby unnecessary power consumption occurs for the vertical blank interval.
To provide an additional description, once a power option has been set by the fixing of a liquid crystal display panel in a process of manufacturing an LCD device, the power option is never changed subsequently, and thus, the same power mode as that in actual outputting of data is being used even in the vertical blank interval.
That is, the data driver of the related art LCD device continuously uses a power portion that has been selected in the manufacturing process of the LCD device, irrespective of the vertical blank interval and active blank interval, and consequently power is unnecessarily consumed during the vertical blank interval.